From EP 2 016 302 B1 a method is known for controlling a pneumatic actuator for the actuation of a pneumatically actuated device, such as a pneumatically actuated starting clutch of a motor vehicle. According to this prior art, the pneumatic actuator comprises a piston arranged to move axially in a pneumatic cylinder, the piston being displaced as a function of a pneumatic pressure in a pressure chamber of the pneumatic cylinder. The pressure in a pressure chamber of the pneumatic cylinder can be adjusted by means of a control valve, itself being actuated by a control device. To increase the pressure in the pressure chamber, the control valve adopts a first position, in which first position compressed air can be passed by way of the control valve into the pressure chamber in order to increase the pressure in the pressure chamber of the cylinder. In contrast, in a second position of the control valve, compressed air can pass out of the pressure chamber toward a pressure medium sink in order to lower the pressure in the pressure chamber.
According to EP 2 016 302 B1 the pneumatic actuator is controlled in such a manner that an intended piston movement direction is preceded by a movement direction opposite to the intended movement direction. In that way, an external force acting on the actuator is increased, whereby possible stick-slip effects can be overcome.
The use of pneumatic actuators for controlling a starting clutch or for controlling clutches or brakes of an automated change-speed transmission imposes strict demands on the dynamics and the control precision.
Until now it has been difficult to fulfill these strict demands without restriction on the dynamics and control precision of pneumatic actuators. Rather, the dynamics of pneumatic actuators have until now been restricted by dead times.
Accordingly, a method is needed for the control of a pneumatic actuator, with which dead times can be reduced.